A position sensor can detect the presence and location of a touch by a finger or by an object, such as a stylus, within an area of an external interface of the position sensor. In a touch sensitive display application, the position sensor enables, in some circumstances, direct interaction with information displayed on the screen, rather than indirectly via a mouse or touchpad. Position sensors can be attached to or provided as part of devices with a display. Examples of devices with displays include, but are not limited to, computers, personal digital assistants, satellite navigation devices, mobile telephones, portable media players, portable game consoles, public information kiosks, and point of sale systems. Position sensors have also been used as control panels on various appliances.
There are a number of different types of position sensors. Examples include, but are not limited to resistive touch screens, surface acoustic wave touch screens, capacitive touch screens, and the like. A capacitive touch screen, for example, may include an insulator coated with a transparent conductor in a particular pattern. When an object, such as a finger or a stylus, touches the surface of the screen there may be a change in capacitance. This change in capacitance may be sent to a controller for processing to determine where the touch occurred on the touch screen.
In a mutual capacitance configuration, for example, an array of conductive drive electrodes or lines and conductive sense electrodes or lines can be used to form a touch screen having capacitive nodes. A node may be formed where a drive electrode and a sense electrode overlap. The electrodes may be separated by an insulator to avoid electrical contact. The sense electrodes may be capacitively coupled with the drive electrodes at the nodes. A pulsed or alternating voltage applied on a drive electrode may therefore induce a charge on the sense electrodes that overlap with the drive electrode. The amount of induced charge may be susceptible to external influence, such as from the proximity of a nearby finger. When an object touches the surface of the screen, the capacitance change at each node on the grid can be measured to determine the position of the touch.
An electrical interconnection between conductive patterns on two surfaces of a substrate 10 is illustrated in FIG. 1. As illustrated in FIG. 1 the substrate 10 may have conductive contact pads 11 and 12 formed at corresponding positions on opposite faces 10a and 10b of the substrate 10. The conductive contact pads 11 and 12 may be connected to respective conductive patterns on the opposite faces 10a and 10b of the substrate 10. An aperture 13 may pass through the substrate 10 and the contact pads 11 and 12. The aperture 13 may be full of a conductive metal 14, so that the conductive metal 14 forms a conductive connection between the contact pads 11 and 12. The aperture 13 may be formed, for example, using a focused laser beam to cut through the substrate 10 and the contact pads 11 and 12. In order to form a reliable conductive connection to each of the contact pads 11 and 12 the conductive metal 14 may extend across and contact the exposed outer faces of the contact pads 11 and 12 in a mushroom, or rivet head, shaped arrangement.
FIG. 8 shows a side view of a touch position-sensing panel 1. The touch position-sensing panel 1 may be formed from a PET substrate 40 having opposing faces 40a and 40b. The PET substrate 40 may have conductive patterns 42 on face 40a of the PET substrate 40 and conductive patterns 41 on an opposite face 40b of the PET substrate 40.
The conductive patterns 42 and 41 may define electrodes similar to the electrodes discussed above with respect to FIG. 1 or connections to such electrodes. The conductive patterns 42 and 41 may define other circuitry. The conductive patterns 42 and 41 are not shown in detail in FIG. 8. The face 40a of the PET substrate 40 may be attached to a transparent covering sheet 43 by a layer of optically clear adhesive 44.
The PET substrate 40 may have an edge 40c. Near to the edge 40c of the PET substrate 40, conductive pattern 41 may define a bond pad region having a number of electrical connectors 45 on face 40b of the PET substrate 40 and the conductive pattern 42 may define a bond pad region having a number of electrical connectors 46 on the opposite face 40a of the PET substrate 40. A double sided flexible printed circuit (FPC) connector 47 connects to electrical connectors 46 and 45. The FPC connector 47 may connect circuits on both opposite faces 40a and 40b of the PET substrate 40 to external circuitry. As shown in FIG. 8, the FPC connector 47 may extend along both opposite sides of the edge 40a of the PET substrate 40 to allow the FPC connector 47 to contact electrical connectors 46 and 45 on opposite faces 40a and 40b of the PET substrate 40. The PET substrate 40 may have a kinked section 48 to provide clearance between the edge 40a of the PET substrate 40 and the optically clear adhesive layer 44 so that the FPC connector 47 can extend between face 40a of the PET substrate 40 and the optically clear adhesive layer 44. The FPC connector 47 may be bonded to the PET substrate 40 by a heat and pressure bonding process.
An example of a stage in the manufacture of a touch position-sensing panel by a reel to reel process is illustrated in FIGS. 10a and 10b, which show a plan view and a side view respectively of a laminated sheet 60. A core of the laminated sheet 60 may be a PET sheet 68 having two opposite faces 68a and 68b. The PET sheet 68 may have a number of conductive patterns 61 formed on face 68a of the PET sheet 68. The conductive patterns 61 may be arranged in a number of lines with the edges of the conductive patterns 61 in each line being aligned. Each conductive pattern 61 may define the electrodes and associated conductors required on face 68a of a PET substrate of a touch position-sensing panel. Each conductive pattern 61 may include a bond pad 62 where electrodes intended to be used to connect the conductive pattern 61 to external circuits may be grouped together. A transparent covering sheet 63 may overlay each of the conductive patterns 61. The transparent covering sheet 63 may be secured to face 68a of the PET sheet 68 by an adhesive layer 64 of optically clear adhesive. The PET sheet 68 may have one or more conductive patterns 65 formed on the opposite face 68b of the PET sheet 68 at locations corresponding to the locations of the conductive patterns 61 on face 68a of the PET sheet 68. The conductive patterns 65 may be arranged in a number of lines with the edges of the conductive patterns 65 in each line being aligned. Each conductive pattern 65 defines the electrodes and associated conductors required on opposite face 68b of a PET substrate of a touch position-sensing panel. Each conductive pattern 65 includes a bond pad 69 (not shown) where electrodes intended to be used to connect the conductive pattern 65 to external circuits may be grouped together. A transparent covering sheet 66 overlies each of the conductive patterns 65 in a line of conductive patterns 65. The transparent covering sheet 66 may be secured to face 68b of the PET sheet 60 by an adhesive layer 67 of optically clear adhesive.
The conductive patterns 61 and 65 and edges of the transparent covering sheets 63 and 66 may be aligned so that the bond pads 62 and 69 are exposed and are not covered by the respective transparent covering sheets 63 and 66.
The illustrated laminated sheet 60 may be formed by a continuous reel to reel process in which a continuous PET sheet 68 bearing conductive patterns 61 and 65 passes between two transparent covering sheets 63 and 66 bearing respective adhesive layers 64 and 67. The transparent covering sheets 63 and 66 and the respective adhesive layers may be adhered to the opposite faces 68a and 68b of the PET sheet 68 to form the laminated sheet 60. The laminated sheet 60 may be rolled onto a reel for storage. A section of the laminated sheet 60 having a single conductive pattern 61 and a single conductive pattern 65 may be cut from the laminated sheet 60 to form a PET substrate for a touch position-sensing panel.